Loads are electrical burdens placed on an electrical system.
When vandwellers talk about loads they usually mean user loads like lighting, running a laptop or microwave. Technically, though, it also includes system loads like charging the bank. Understanding this last part will help make power rationing and load timing easier to implement.
Parasitic (or vampire) loads are tiny, continuous loads that can deplete the bank's state of charge. The classical example is a device like a USB outlet that uses power internally whether or not anything is plugged into it. Some inverters, solar charge controllers, and voltage-sensing isolators can have significant parasitic draws.